基于SPEI的中国干湿变化趋势归因分析

选用1960—2012年中国气象站点资料,利用标准化降水蒸散指数SPEI(Standardized Precipitation Evapotranspiration Index),研究了中国干湿变化趋势及其原因。过去52 a,中国干湿变化由西北向东南呈现"+-+"的空间分布状况,其中黄河流域、长江流域西部、西南流域东南及珠江流域西部显著变干;淮河流域中西部和西北流域大部显著变湿;通过数值试验,定量计算了参考蒸散发及降水对干湿趋势的贡献状况。就中国总体而言,年平均参考蒸散发显著减少抵消了由年降水量减少导致的干化趋势,呈微弱变湿趋势;其次,降水仍然是多数区域干湿变化的主导因素(黄河流域中部、长江流域、西南流域、珠江流域及东南流域);同时,参考蒸散的影响值得引起注意,其在辽河流域、海河流域、淮河流域及西北流域对干湿趋势的贡献均超过降水贡献。

Attribution analysis of dryness/wetness change over China based on SPEI

Using meteorological observation data at weather stations in China from 1960 to 2012, the trend of dryness/wetness changes and its reasons were analyzed based on SPEI (Standardized Precipitation Evapotranspiration Index). Over the past 52 years, the dryness/wetness changes showed a "+-+" spatial distribution from northwestern to southeastern China. Most of the northwestern River Basin (NWRB) and western Huaihe River Basin (HaRB) significantly tend to be wet, while the Yellow River Basin (YRB), western Changjiang River Basin (CJRB), southeastern southwestern River Basin (SWRB) and western Pearl River Basin (PRB) have significant increase in dryness. The contribution of referenced evapotranspiration (ET₀) and precipitation to dryness/wetness changes were quantitatively calculated by several numerical experiments. Results show that the average annual ET₀ significantly offsets the drying trend caused by the decrease in annual precipitation, showing a trend of slight wetting. Precipitation is still the dominant factors for the dryness/wetness changes in most regions (the central YRB CJRB, SWRB, PRB and SERB). The impacts of ET₀ on dryness/wetness are worth attention. The contribution of ET₀ to the dryness/wetness trend in Liao River Basin (LRB), Hai River Basin (HRB), HaRB and NWRB exceeds that of precipitation.